Chest compressions provided as a component of cardiopulmonary resuscitation (CPR) should be accomplished at a consistent depth of about 2 inches, according to the CPR Guidelines 2010. This is difficult to accomplish, especially over a long course of CPR. Chest compression monitors, such as those used in ZOLL Medical Corporation's CPR-D-padz® and Real CPR Help® chest compression monitor, give real time feedback to a CPR provider, measuring the depth and rate of compressions achieved during CPR and providing immediate reports of achieved chest compression depth to the CPR provider. This helps the CPR provider achieve the desired compression depth and also helps the CPR provider realize when he is too fatigued to provider proper chest compressions. In use, the chest compression monitor is sandwiched between the chest of a cardiac arrest victim and the hands of a CPR provider during compressions. These chest compression monitors are free-floating, and can accurately measure chest compression depth without reference to any external reference or input. This is described in Halperin, et al., CPR Chest Compression Monitor, U.S. Pat. No. 6,390,996 (May 21, 2002), as well as Palazzolo, et al., Method of Determining Depth of Chest Compressions During CPR, U.S. Pat. No. 7,122,014 (Oct. 17, 2006). Nonetheless, these chest compression monitors can be augmented with reference sensors, to ensure or improve accuracy when chest compressions are performed on a patient that is coincidentally subject to gross vertical movements. For example, Palazzolo, et al., Method of Determining Depth of Chest Compressions During CPR, U.S. Pat. No. 7,122,014 (Oct. 17, 2006) disclosed a system including a chest compression monitor disposed on the chest of a cardiac arrest victim and a reference sensor disposed elsewhere on the body of the cardiac arrest victim or a gurney supporting the cardiac arrest victim.
For adults, CPR chest compressions are delivered while the patient is supine, supported by a sufficiently rigid surface (a floor, gurney, or hospital bed). For infants, CRP chest compressions are provided with one of two methods. The preferred method is the two-thumb method, and entails grasping the infant's thorax with both hands, placing both thumbs over the sternum (with the fingers supporting the back of the infant) and compressing the sternum with the thumbs. Another method, suggested for use by a lone rescuer, is referred to as the two-finger method, and entails compression of the infant's chest with two fingers placed over the inter-mammary line (superior to the xiphoid process). Compressions should be about 1.5 inches (3.8 cm) (one third of the thickness of the thorax of 4.5 inches (11.4 cm), which is rough estimate of infant chest thickness which is of course variable depending on the age of the infant patient). The chest should be released completely after each compression. According to the American Heart Association, the 2-thumb-encircling hands technique is preferred over the 2-finger technique because it produces higher coronary artery perfusion pressure, results more consistently in appropriate depth or force of compressions, and may generate higher systolic and diastolic pressures.
In another aspect of CPR, active compression-decompression CPR has been suggested as an adjunct to CPR. Active compression-decompression refers to compression techniques which include some mechanism for actively lifting the chest wall between compression down strokes, rather than merely relying on the natural resilience of the chest wall to expand the chest between compressions. Active decompression devices, such as proposed by Steen, Systems and Procedures for Treating Cardiac Arrest, U.S. Pat. No. 7,226,427 (Jun. 5, 2007), use a piston to compress the chest. The piston is driven up and down by a motor. A suction cup on the lower face of the piston is intended to pull the chest wall up with the piston. Active decompression is not yet recommended for pediatric use.